1. Field of the Invention
This invention relates to a magnetic tape guide apparatus for guiding a magnetic tape.
2. Description of the Related Art
A magnetic tape guide apparatus is incorporated in various magnetic recording and/or reproducing apparatus in which a magnetic tape is employed as a magnetic record medium. An example of such magnetic recording and/or apparatus is a video tape recorder. An example of a conventional magnetic tape guide apparatus for use with a video tape recorder is shown in FIG. 22. Referring to FIG. 22, the magnetic tape guide apparatus shown includes a magnetic head drum 3 including a pair of upper and lower magnetic tape guide drums 1 and 2 having an equal diameter which are disposed on a common axis. A magnetic tape 4 is guided obliquely along a circumferential face of the magnetic head drum 3 while recording onto or reproduction from the magnetic tape 4 is performed by a rotary magnetic head 5 located between the drums 1 and 2.
The magnetic tape guide apparatus further includes a fixed guide pin 6 disposed intermediately of the path of the magnetic tape 4 for guiding the magnetic tape 4.
One of the guide drums 1 and 2 of the magnetic head drum 3, for example, the drum 1, is formed as a rotary drum while the other drum 2 is formed as a fixed drum.
When the magnetic tape 4 is guided by the guide pin 6 and the guide drums 1 and 2 each formed from a columnar or cylindrical member (such guide elements may each be hereinafter referred to as guide member), one of the significant problems is reduction of the transport performance of the magnetic tape 4 which is caused by sticking of the magnetic tape to any of the guide members, particularly by sticking when the guide member is in a fixed condition and the magnetic tape is guided in a slidably contacting condition with the guide member.
Meanwhile, in the field of magnetic recording, the requirement for higher density recording is increasing year by year. In this instance, there is a tendency that thin metal film magnetic tapes are used wherein a magnetic layer is formed by vapor deposition, sputtering or the like of magnetic metal having a high coercive force such as Co--Ni, Co--Cr or Co--O type metal.
In addition, the form of the signal to be recorded is being changed from an analog signal to a digital signal, and designing a record medium in accordance with the digital signal form together with an increase in the recording density is required.
Normally, a so-called in-plane magnetic recording method wherein a magnetic record medium having a more easily magnetized axis in the plane of the recording medium is employed. However, with the in-plane magnetic recording method, the magnetization directions of magnetization sections on the magnetic record medium are arranged such that, as the recording density increases, adjacent magnetization sections repel each other by an increasing repulsive force. Accordingly, there naturally is a limitation in the increase of the recording density, and it is difficult to achieve recording of a required high density.
Further, in the in-plane magnetic recording method, there is a drawback in that, as the distance of reversals of magnetization in a pattern in which a reversal of magnetization repeats twice decreases, that is, as the recording density increases, peak shifts caused by magnetization repulsion and waveform interference increase, and consequently the error rate increases.
Thus, in recent years, remarkable development has been made to perpendicular magnetic recording methods which employ a magnetic record medium having a magnetization-easy axis in a perpendicular direction to the plane of a film of the magnetic record medium.
With the perpendicular magnetic recording method, there is little demagnetizing action compared to the in-plane magnetic recording method, and it is possible to remarkably increase the recording density.
As a magnetic record medium for digital signals to be recorded or reproduced in accordance with the perpendicular magnetic recording method, a magnetic thin metal film magnetic tape of the Co--Ni, Co--Cr or Co--O type which has a superior magnetic characteristic as a perpendicular magnetic record medium or a magnetic film wherein a protective film of carbon or ZnO.sub.2 for assuring a high durability and corrosion resistance is provided on a magnetic thin metal film is used.
However, when such a thin metal film magnetic tape is used, since the magnetic tape has a smooth surface, sticking of the magnetic tape to a guide drum or a guide pin of a magnetic tape guide apparatus, which may be caused by an increase of the frictional resistance, causes significant problems compared to a magnetic tape having an applied magnetic layer type.
In such a magnetic tape guide apparatus, the countermeasure for the problem of sticking of a magnetic tape to a guide drum or a guide pin, particularly to a fixed guide drum or a fixed guide pin which guides a magnetic tape in a slidably contacting condition, is normally provided by appropriate selection of a metal material constituting the guide drum or the guide pin (guide member), roughening of the surface of the guide member and so forth.
In particular, roughening of the surface of a guide member so that fine grooves are formed in the circumferential direction of the guide member is performed normally by working a circumferential face of a tubular metal member to be used as the guide member using a cutting tool, and as regards the surface performance of the guide member, various designs have been attempted only as to the height of crests of the concave and convex configuration provided by the fine grooves, that is, a so-called maximum surface height .delta.(Rmax), as shown in FIG. 1 in which an enlarged section of the guide member at the circumferential guide face 11 for a magnetic tape is schematically shown.
However, even with such means, sticking of a magnetic tape to a magnetic tape guide apparatus still remains as a problem in a high humidity condition particularly for a magnetic recording and reproducing apparatus which is to achieve reduction particularly of the error rate and particularly an error rate on the order of 10.sup.-5.